Since Apple doesn't have anything resembling a monopoly in any market it operates in, and since all DoJ can do is file a suit that is predicated on them having one, this is unlikely to go anywhere.
It's hard to prove, though, because it tends to require showing that the company did the tying solely or mainly for the purpose of restraining trade, as opposed to for some legitimate purpose. The car manufacturers lost because the courts didn't buy their argument that their attempts to limit the replacement-parts market were for quality-assurance reasons. Apple would have to argue that section 3.3.1 isn't intended mainly or solely to stop cross-platform compatibility, but has some legitimate, non-trade-restraining purpose, like improving the reliability or quality of iPhone apps. Probably even just "it makes it easier for us to review apps if they're all in the same languages" would be a good enough explanation. A bad result would be a leaked smoking-gun email saying "hey we should institute this policy to stop people from porting our apps to Android".
Monopoly leveraging is a separate (but related) concept, as far as I understand it, and a bit easier to prove, because there's a much stronger presumption that if it's happening, it's bad, regardless of the reasons.
(Edit: edited/expanded a bit for clarity)
Remember when he replied to that blogger saying he agreed with Gruber followed by something sort of like the above? Would be mighty ironic if one if his tiny glib emails ended up taking down the company.
Forcing Apple to repeal 3.3.1 doesn't allow offending software to be built and sold (as it already can be), it forces Apple to stock its shelves with it and thus take on users' expectations that Apple will support it (by making sure an OS update doesn't break hundreds of apps by running afoul of a popular middleware package).
Where else exactly could they go?
>> Forcing Apple to repeal 3.3.1 doesn't allow offending software to be built and sold (as it already can be), it forces Apple to stock its shelves with it
Those two things are the same, by Apple's design.
Those certainly aren't remotely equivalent options, but my point was just that 3.3.1 is about Terms of Use for the App Store, not an attempt to legally stifle an existing secondary market as with car parts and ink cartridges.
It's thus a qualitatively different situation.
More relevant precedent might be found by looking at other situations where service providers have added terms to limit allowed devices/tools.
But, as a counterexample, I'm not aware of a successful suit that challenged HP's use of printer cartridge rights management technology.
If i have an xbox, I can get a game from Best Buy or Amazon, etc. Even though those are closed systems.
If I have an iPhone, I can only get apps from the Apple store.
I'm not positive if this is unique to Apple in the mobile space or not. I know I can get blackberry apps from anywhere, same with WinMo. I'm not sure about Android or Palm.
That may not qualify as a "relevant market" for determining monopoly status. (The Conclusions of Law from the MS v DOJ case makes interesting reading along these lines).
http://www.justice.gov/atr/cases/f218600/218633.htm
Whether this zone of commercial activity actually qualifies as a market...depends on whether it includes all products "reasonably interchangeable by consumers for the same purposes." ..."Because the ability of consumers to turn to other suppliers restrains a firm from raising prices above the competitive level, the definition of the 'relevant market' rests on a determination of available substitutes."
So if a plaintiff were to try to argue that Apple is the sole supplier of App Stores for iPhones, it would become germane that nothing is charged for access to this service, and that if access became expensive consumers could flee to other smart phones.